Hollow package and method for fabricating the same and solid-state image apparatus provided therewith

ABSTRACT

A hollow package includes a package body composed of an epoxy resin having a low thermal coefficient of linear expansion, wherein the package body includes a recess for receiving an electronic component, and leads, for extracting electrodes of the electronic component, extending from the inner surface of the recess, via the upper surface of the package body, to the peripheral surface, and a transparent sealing plate bonded onto the upper surface of the package body with an ultraviolet-curable resin.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hollow package, particularly a hollowpackage in which a package body having a recess is sealed with atransparent sealing plate, and also relates to a method for fabricatingthe same.

2. Description of the Related Art

A solid-state image apparatus of a typical leadless chip carrier (LCC)generally has a structure, as shown in FIG. 4, in which a ceramicpackage body having a recess with a step receives a solid-state imagedevice, and the package body is sealed with a glass plate. In thedrawing, symbol a represents a first layer of the ceramic package, whichis flat, and a metallized lead d is formed thereon, extending from theside to the outer bottom. Symbol b represents a second layer of theceramic package, which is in the shape of a rectangular frame, and ametallized lead d is formed thereon, extending from the upper surface tothe side, and also connecting to the lead d on the first layer a. Symbolc represents a third layer of the ceramic package, which is in the shapeof a rectangular frame, and an opening of the third layer c is largerthan an opening of the second layer b. The two openings form a recess e,for receiving a solid-state image device, having a step with the firstlayer a serving as the inner bottom.

Symbol f represents a solid-state image device received in recess e onthe ceramic package, symbol g represents bonding wires connectingbetween electrodes of the solid-state image device f and the metallizedleads d, and symbol h represents a transparent sealing plate composed ofglass bonded onto the upper surface of the package with an adhesive itherebetween for sealing the recess e.

Next, a method for fabricating the package will be described. Unsinteredpackage sheets a, b, and c (corresponding to the first layer a, secondlayer b, and third layer c), which are so-called “green sheets” or“green ceramic sheets”, are prepared. The green lead d is formed on theindividual sheets a and b. The individual sheets a, b, and c aredeposited at predetermined positions and are sintered, whereby, thepackage body is obtained. Next, the metallized lead d is formed byplating, and die bonding is performed to the solid-state image device f,followed by wire bonding. Lastly, the transparent sealing plate hcomposed of glass is bonded onto the upper surface of the package body.Thus, a solid-state image apparatus is complete, in which thesolid-state image device is received in the ceramic hollow package.

Because of the high cost of materials and processing for ceramic hollowpackages, it has been difficult to reduce the fabrication costs ofsolid-state image apparatuses. Therefore, the present inventor andothers have made attempts to fabricate hollow packages from a resininstead of ceramic by applying the molded interconnect device (MID)technique widely used in various electronic devices to hollow packages.This is because an MID is an electronic component in which a circuit(three-dimensional circuit) is formed on a three-dimensional partproduced by injection molding, and a resin material which isconsiderably less expensive in comparison with a ceramic material isused, and also the inexpensive injection molding technique which iseasier and faster than sintering is used for formation. In particular,it is greatly advantageous that injection molding be performed once toenable the formation of a package body even in the case of athree-dimensional part, which is in contrast to the complex fabricationof a ceramic hollow package requiring the steps of forming three-layersof green sheets, depositing them at correct positions, and sintering.

The current MID technique, however, has been found to be unsuitable forhollow packages which receive semiconductor devices such as solid-stateimage devices. The reason is that in the general MID, a thermoplasticresin having a high thermal coefficient of linear expansion, forexample, a liquid crystal polymer (LCP) or PPS, is used, and there is alarge difference in thermal coefficient of linear expansion between thethermoplastic resin and glass used as the transparent sealing plate.Therefore, if the hollow package is sealed with the transparent sealingplate, either the sealing plate or the resin forming the package bodywill be easily cracked, resulting in difficulty in maintainingair-tightness.

Also, since leads, i.e., lands, and areas between leads, i.e., spaces,intervene between the transparent sealing plate and the package bodywhich are to be bonded together, if the general adhesion technique usinga thermosetting resin is employed, an internal pressure between thepackage body and the transparent sealing plate increases because of theheating for adhesion, resulting in air leakage through the spaces of thelands-and-spaces. This also does not allow air-tightness to bemaintained.

In the case of a ceramic hollow package, since a plurality of sheetshaving a lead on the surface are deposited, a lead for connectingbetween the interior of the hollow package and the exterior can beformed even without placing wires on the upper surface of the hollowpackage. On the other hand, in the case of a package body formed byusing the MID technique, unless a through-hole is formed on the packagebody, and the interior of the package body and the external lead areconnected via the through-hole, the lead must be formed on the surfaceof the package body, and thus, the lead inevitably runs on the uppersurface of the package body which is the connecting section between thepackage body and the transparent sealing plate. As a result, thelands-and-spaces are formed on the upper surface of the package. Thethickness of the spaces is substantially equal to the thickness of thelead, for example, 20 to 30 μm. Generally, since a thermosetting resinis used as the adhesive, if the conventional technique is followed, heattreatment must be performed to generate adhesive bonding in the adhesivematerial. If heat treatment is performed, the internal pressure withinthe hollow package increases inevitably and even if a resin for adhesionis buried in the spaces, air leakage occurs, and thus, it is impossibleor extremely difficult to maintain air-tightness.

SUMMARY OF THE INVENTION

As described above, it seemed impossible to apply the MID technique to ahollow package, in which a semiconductor device such as a solid-stateimage device placed in a package body is sealed with a transparentsealing plate, for example, glass. However, the present inventorcontinued to investigate in order to overcome the difficulty, andfinally achieved the present invention.

It is an object of this invention to provide a method for fabricating ahollow package with a resin, in which an electronic component, forexample, a semiconductor device, placed in a recess on a package body issealed with a transparent sealing plate, such that the cost of materialsand processing is reduced and the price of an electronic apparatus (forexample, a solid-state image apparatus) provided with the hollow packageis reduced.

In accordance with one aspect of the present invention, a hollow packageincludes a package body having an MID structure composed of an epoxyresin having a low thermal coefficient of linear expansion and atransparent sealing plate which is bonded onto the upper surface of thepackage body with an ultraviolet-curable resin. The package bodyincludes leads, for extracting electrodes of a contained electroniccomponent, which extend from the inner surface of a recess, via theupper surface of the package body, to the peripheral surface. Thetransparent sealing plate protects the recess on the package body fromthe exterior.

In accordance with the hollow package of the present invention, firstly,since the epoxy resin having a low thermal coefficient of linearexpansion is used as a material to form the package body, the differencein thermal coefficient of linear expansion between the transparentsealing plate and the package body can be minimized, and even if theinterior of the hollow package is sealed with the transparent sealingplate, the transparent sealing plate or the resin forming the packagebody is not easily cracked by thermal stress, enabling air-tightness tobe maintained.

Secondly, since the ultraviolet-curable resin is used as the adhesivefor bonding the package body and the transparent sealing plate together,no heating is required in order to generate adhesive bonding.Accordingly, it is possible to maintain air-tightness since there is noheating which may increase the internal pressure between the packagebody and the transparent sealing plate and thus may cause air leakagethrough the spaces in the lands-and-spaces described above.

Thirdly, since the package body is composed of a resin which is lessexpensive in comparison with ceramic, the cost of materials can bereduced, and also since the package body is formed by injection moldingwhich does not require the deposition of green sheets or sintering, thecost of formation can also be reduced. Accordingly, the price of anelectronic apparatus provided with the hollow package can be reduced.

In accordance with another aspect of the present invention, a method forfabricating a hollow package includes the steps of forming a packagebody by three-dimensional injection molding of an epoxy resin having alow thermal coefficient of linear expansion; roughening a surface of thepackage body; forming a wiring layer by electroless plating; formingleads by patterning the wiring layer; receiving an electronic componentinto a recess of the package body and connecting electrodes of theelectronic component to the leads; and then bonding a transparentsealing plate onto an upper surface of the package body with anultraviolet-curable resin.

In accordance with the method for fabricating the hollow package, sincethe package body is composed of a resin which is less expensive incomparison with ceramic, the cost of materials can be reduced, and alsosince the package body is formed by injection molding which does notrequire the deposition of green sheets or sintering, the cost offormation can also be reduced. Accordingly, the price of an electronicapparatus provided with the hollow package can be reduced.

Since the surface of the package body is roughened after the formation,adhesiveness of the wiring layer subsequently formed can be increased,and the bond strength of the transparent sealing plate to be bonded tothe hollow package can be increased. Also, because of the roughening,connectivity between the leads and, connectors, for example, connectingwires, can be strengthened.

In accordance with still another aspect of the present invention, asolid-state image apparatus includes a package body composed of an epoxyresin having a low thermal coefficient of linear expansion and atransparent plate bonded onto the upper surface of the package body. Thepackage body includes a recess for receiving a solid-state image device,and leads, which are connected to electrodes of the solid-state imagedevice, extending from the inner surface of the recess, via the uppersurface of the package body, to the peripheral surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a hollow package as a firstembodiment of the present invention;

FIG. 2A is an assembly view of the first embodiment shown in FIG. 1, and

FIG. 2B is a perspective view showing a bottom surface of the firstembodiment;

FIGS. 3A through 3I are sectional views which show step by step anexample of a method for fabricating the hollow package shown in FIGS. 1,2A and 2B (i.e., a method of fabricating a hollow package as a firstembodiment of the present invention); and

FIG. 4 is a sectional view of a conventional hollow package.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A hollow package in accordance with the present invention includes apackage body having an MID structure composed of an epoxy resin having alow thermal coefficient of linear expansion, wherein the package bodyincludes a recess for receiving an electronic component and leads forextracting electrodes of the electronic component, and the leads extendfrom the inner surface of the recess via the upper surface, to theperipheral surface. The hollow package also includes a transparentsealing plate for protecting the recess of the package body from theexterior, wherein the sealing plate is bonded onto the upper surface ofthe package body with an ultraviolet-curable resin. A suitable exampleof the electronic component is a semiconductor device such as asolid-state image device, which is used as an area sensor or a linesensor; however, the electronic component is not limited to the above.For example, a light-emitting device may be used. A typical recessincludes an inner bottom to which a semiconductor device is bonded and astep having a bonding area which lies outside the inner bottom and onestep higher up, however, the recess is not limited to this, and thenumber of steps may be greater. The leads may be composed of any metalas long as it can be applied onto the surface of the resin forming thepackage body by electroless plating, or it can be applied onto theelectroless-plated underlying layer by electroless plating orelectroplating, and has proper conductivity. Also, the leads may besingle-layered or multi-layered. Specifically, the leads may bemulti-layered, composed of copper onto which nickel and gold are plated,or may be composed of gold or the like.

Preferably, the thermal coefficient of linear expansion of the epoxyresin having a low thermal coefficient of linear expansion is 13 ppm orless. The reason is that this is relatively close to the thermalcoefficient of linear expansion of glass, i.e., 5 to 7 ppm, which hassignificantly high transparency and is most commonly used for opticalpurposes, and cracks do not easily occur by thermal stress in thetransparent sealing plate or the package body, and in the electroniccomponent in the package body. By three-dimensional injection molding ofthe epoxy resin, the package body for the hollow package is formed.

A method for fabricating a hollow package in accordance with the presentinvention includes the steps of forming a package body having a recessby three-dimensional injection molding of an epoxy resin having a lowthermal coefficient of linear expansion; roughening the entire surfaceof the package body; forming a wiring layer entirely onto the surface ofthe package body by electroless plating; forming leads by patterning thewiring layer by means of exposure using a resist, development, andselective etching; receiving an electronic component into the recess andconnecting electrodes of the electronic component to the leads; andthen, bonding a transparent sealing plate onto the upper surface of thepackage body with an ultraviolet-curable resin. The roughening of thesurface of the package body may be performed, for example, by immersingthe package body in a liquid that erodes the resin for an appropriateperiod of time, or may be performed by physical means or any othermeans.

The present invention will be described in detail with reference toembodiments shown in the drawings. FIG. 1 is a sectional view showing ahollow package as a first embodiment of the present invention, and FIG.2A is an assembly view of the same. In the drawings, numeral 1represents a package body composed of an epoxy resin having a lowthermal coefficient of linear expansion formed by an MID technique, thatis, by three-dimensional injection molding. The thermal coefficient oflinear expansion of the epoxy resin is, for example, 13 ppm or less.Numeral 2 represents a recess of the package body 1, numeral 3represents the inner bottom of the recess as a solid-state image devicebonding area, and numeral 4 represents a step of the recess 2. Numeral 5represents the upper surface of the package body, and a portion betweenthe upper surface 5 and the step 4, that is, an upper inner side, and aportion between the step 4 and the inner bottom 3, that is, a lowerinner side, are both inclined planes, with an inclination of, forexample, approximately 30 degrees in relation to the vertical. The innersides are inclined so that there is no shade other than a photomaskcaused by exposure light when exposure is performed in order to patternthe leads.

Numeral 6 represents leads formed on the surface of the package body,which are formed, for example, by plating nickel (with a thickness of,for example, 3 μm) onto the surface of copper (with a thickness of, forexample, 10 μm), and by further plating gold (with a thickness of, forexample, 0.3 μm) onto the surface of the nickel-plated layer. Theindividual leads 6 extend from the bottom of the hollow package 1, theouter surface, the upper surface 5, the upper inner side, to the step 4.The ends of the individual leads 6 lying on the step 4 are connected tothe ends of a connecting wires 8 which are described below.

Numeral 7 represents a solid-state image device, for example, for a linesensor, mounted on the inner bottom of the package body 1 by diebonding. Numeral 8 represents connecting wires for connecting betweenelectrodes of the solid-state image device 7 and the ends of the leads6, which are composed of, for example, gold or aluminum. Numeral 9represents a transparent sealing plate composed of glass, which isbonded onto the upper surface of the package body 1 with an adhesive 10composed of an ultraviolet-curable resin. FIG. 2B is a perspective viewshowing a bottom surface of the package body 1 of the embodiment.

In accordance with the hollow package of the present invention, firstly,since the epoxy resin having a low thermal coefficient of linearexpansion is used as the package body 1, the difference in thermalcoefficient of linear expansion between the transparent sealing plate 9and the package body 1 can be minimized, and even if the interior of thehollow package is sealed with the transparent sealing plate 9, thetransparent sealing plate 9 or the resin forming the package body 1 isnot easily cracked by thermal stress, enabling air-tightness to bemaintained.

Secondly, since the ultraviolet-curable resin 10 is used as the adhesivefor bonding the transparent sealing plate 9 composed of glass onto theupper surface 5 of the package body 1, ultraviolet rays are radiated inorder to generate adhesive bonding, and heating is not required.Accordingly, it is possible to maintain air-tightness since there is noheating which may increase the internal pressure between the packagebody and the transparent sealing plate and thus may cause air leakagethrough the spaces in the lands-and-spaces of the leads 6.

Thirdly, since the package body is composed of a resin which is lessexpensive in comparison with ceramic, the cost of materials can bereduced, and also since the package body is formed by injection moldingwhich does not require either the deposition of green sheets orsintering, the cost of formation can also be reduced. Accordingly, theprice of a device, for example, a line sensor, provided with the hollowpackage can be reduced.

FIGS. 3A through 3I are sectional views which show the main process offabricating the hollow package shown in FIG. 1.

(A) As shown in FIG. 3A, a package body 1 is prepared. A plurality ofpackage bodies 1 for a plurality of line sensors are fabricated in onepiece. The adjacent package bodies 1 and 1 adjoin each other at theouter sides. A portion to be a line of the lead 6 corresponds to athrough-hole 11, and a portion to be a space corresponds to a-spacebetween the adjacent through-holes 11 and 11, which connects the packagebodies 1 and 1. At the final stage, the resin is cut along the linepassing through the through-hole 11 to separate the adjacent packagebodies 1 and 1.

(B) Next, the package body 1 is immersed in an eroding liquid, forexample, a chlorine-based etching liquid, in order to roughen the entiresurface of the package body 1, as shown in FIG. 3B, and then, a catalystis applied onto the surface to assist plating.

(C) Next, as shown in FIG. 3C, a wiring layer (with a thickness of, forexample, 10 μm) 6 composed of copper is formed by plating. Since thisplated layer is formed onto the surface of the package body 1 that is aninsulator, electroless plating is performed.

(D) Next, a positive resist 12 is applied onto the surface of the lead6, and the resist 12 is patterned by exposure and developmenttreatments, as shown in FIG. 3D.

(E) Next, with the patterned resist 12 as a mask, etching is performedonto the wiring layer 6 composed of copper to produce the lead 6. Then,the resist 12 used as the mask is removed. FIG. 3E shows a state inwhich the resist has been removed.

(F) Next, as shown in FIG. 3F, nickel is plated (with a thickness of,for example, 3 μm) onto the lead 6, and further, gold is plated (with athickness of, for example, 0.3 μm).

(G) Next, a solid-state image device 7 is mounted on the inner bottom 3of the package body 1, and then, wire (8) bonding is performed. FIG. 3Gshows a state in which wire bonding has been performed.

(H) Next, an ultraviolet-curable resin 10 is applied onto the uppersurface 5 of each package body 1, a transparent sealing plate 9 composedof glass is placed onto the upper surface 5 of each package body 1, andthen, as shown in FIG. 3H, the ultraviolet-curable resin 10 isirradiated with ultraviolet rays through the transparent sealing plate 9so that the package body 1 and the ultraviolet-curable resin 10 arebonded together.

(I) Next, by cutting apart the package bodies 1 and 1, individual linearsensors are separated. FIG. 3I shows an independent linear sensor.

In accordance with the method for fabricating the hollow package of thepresent invention, since the package body 1 is composed of a resin whichis less expensive in comparison with ceramic, the cost of materials canbe reduced, and also since the package body is formed by injectionmolding which does not require either the deposition of green sheets orsintering, the cost of formation can also be reduced. Accordingly, theprice of an apparatus, for example, a linear sensor, provided with thehollow package can be reduced.

Also, since the surface of the package body 1 is roughened after theformation, adhesiveness of the wiring layer 6 subsequently formed can beincreased, and the bond strength of the transparent sealing plate 9 tobe bonded to the package body 1 can be increased. Also, because of theroughening, connectivity between the leads 6 and the connecting wires 8to be connected can be strengthened.

In accordance with the hollow package of the present invention, firstly,since the epoxy resin having a low thermal coefficient of linearexpansion is used as the adhesive for bonding the package body and thetransparent sealing plate together, the difference in thermalcoefficient of linear expansion between the transparent sealing plateand the package body can be minimized, and even if the interior of thehollow package is sealed with the transparent sealing plate, thetransparent sealing plate or the resin forming the package body is noteasily cracked by thermal stress, enabling air-tightness to bemaintained.

Secondly, since the ultraviolet-curable resin is used as the adhesivefor bonding the transparent sealing plate and the package body together,heating is not required in order to generate adhesive bonding.Accordingly, it is possible to maintain air-tightness since there is noheating which may increase the internal pressure between the packagebody and the transparent sealing plate and thus may cause air leakagethrough the spaces of the lands-and-spaces of the leads running on theupper surface of the package body.

Thirdly, since the package body is composed of a resin which is lessexpensive in comparison with ceramic, the cost of materials can bereduced, and also since the package body is formed by injection moldingwhich does not require either the deposition of green sheets orsintering, the cost of formation can also be reduced. Accordingly, theprice of an electronic apparatus provided with the hollow package can bereduced.

In accordance with the method for fabricating the hollow package of thepresent invention, since the package body is composed of a resin whichis less expensive in comparison with a ceramic, the cost of materialscan be reduced, and also since the package body is formed by injectionmolding which does not require the deposition of green sheets orsintering, the cost of formation can also be reduced. Accordingly, theprice of an electronic apparatus provided with the hollow package can bereduced.

Also, since the surface of the package body is roughened after theformation, adhesiveness of the wiring layer subsequently formed can beincreased, and the bond strength of the transparent sealing plate to bebonded to the package body can be increased. Also, because of theroughening, connectivity between the wiring layer and the connectingwires to be connected can be strengthened.

What is claimed is:
 1. A hollow package comprising: an elongated packagebody comprising an epoxy resin having a low thermal coefficient oflinear expansion than that of a transparent sealing plate, said packagebody comprising a recess for receiving an elongated electroniccomponent, and leads extending from the inner surface of said recess,via the upper surface of said package body, to the peripheral surface,said leads being connected to electrodes of said electronic component;and said transparent sealing plate bonded onto the upper surface of saidpackage body with an ultraviolet-curable resin.
 2. A hollow packageaccording to claim 1, wherein said low thermal coefficient of linearexpansion is 13 ppm or less.
 3. A hollow package according to claim 1,wherein at least one surface of said package body is roughened.
 4. Ahollow package according to claim 1, wherein the inner surface of saidrecess is inclined in relation to the vertical.
 5. A hollow packageaccording to claim 1, wherein said electronic component is a solid-stateimage device adapted to be connected to said leads.
 6. A solid-stateimage apparatus comprising: an elongated package body comprising anepoxy resin having a low thermal coefficient of linear expansion thanthat of a transparent sealing plate, said package body comprising arecess for receiving an elongated solid-state image device, and leadsextending from the inner surface of said recess, via the upper surfaceof said package body, to the peripheral surface, said leads beingconnected to electrodes of said solid-state image device; and saidtransparent plate bonded onto the upper surface of said package bodywith an ultraviolet-curable resin.
 7. A solid-state image apparatusaccording to claim 6, wherein said low thermal coefficient of linearexpansion is 13 ppm or less.
 8. A solid-state image apparatus accordingto claim 6, wherein at least one surface of said package body isroughened.
 9. A solid-state image apparatus according to claim 6,wherein the Inner surface of said recess is inclined in relation to thevertical.